#include<bits/stdc++.h>
#define sd(n) scanf("%d",&n) 
#define sld(n) scanf("%lld",&n)
#define pd(n) printf("%d", (n))
#define pld(n) printf("%lld", n)
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define fi first
#define se second
const int N=2e5;
#define INF 0x7fffffff
typedef long long int ll;
using namespace std;
//----------------------------------------------------------------------------//
void solve()
{
	ll a = 1, b = 1,n;
    sld(n);

    ll t1,t2=0;
    if(n>20) n=20;
    for (int i = 0; i <=n; i ++ )
    {
        if(i==n-1) t1=a;
        if(i==n) t2=a;
        ll c = a + b;
        a = b, b = c;
    }
    printf("%.8lf",(double)t1/t2);
}

int main()
{
	int T=1;
	//sd(T);
	while (T--)
	{
		solve();
	}
	return 0;
}